Lightweighting Special Coverage: Light, Strong and Printed

Advances in additive manufacturing technology can potentially result in the proliferation of more lightweight, printed parts.

The term that used to be used quite frequently to describe the various processes by which parts, components, tools and other objects are created by building rather than taking away (adding rather than subtracting) is “rapid prototyping.” Then “3D printing” became more common. And there is yet another term used, one that in some ways sounds more serious and substantial, “additive manufacturing.” Taking a blank of aluminum or steel and then applying a milling or a turning machine to it is, consequently, “subtractive manufacturing.”)

While there is certainly an advantage, in some cases, in terms of time (the “rapid” portion of the term), there can also be an advantage in terms of weight when using the additive manufacturing approach.

That is, structures can be created with shapes and materials that otherwise couldn’t be produced: there can be voids or lattices in areas that would be difficult—if not infeasible—to produce using conventional, subtractive approaches.

One of the companies that has been working in the rapid/3d/additive arena since essentially its inception is Stratasys (stratasys.com). Its CEO Ilan Levin admits that the market is maturing and that much of what is going on in the technology has tended to be more incremental than breakthrough. So the company began to look at the ways to get a step-function change in what it could provide to the market.

And to that end, it met with people including Dr. Ellen Lee, technical leader, Advanced Manufacturing Research, Ford Motor Co., and Teri Finchamp, director of Operations and Quality, Boeing Phantom Works.

The company has long had two technologies. There’s fused deposition modeling (FDM). In this process, there is a layer by layer buildup of parts: there is a spool of thermoplastic material that’s fed through a printer head that heats the material and then deposits it in the form of ultrafine beads. There is PolyJet printing that has a series of print heads mounted on a carriage along with UV lights; the print heads deposit UV-curable plastic as required.

It set about to develop something new, something that would allow what Lee describes as “design to function—designing something not limited by manufacturing constraints.”

The Stratasys team came up with two such things, two demonstration systems that can make stronger, lighter and, in one case, significantly bigger objects.

There is the Infinite-Build 3D system. This system, which uses FDM extrusion, operates so that the printing is performed on a vertical plane rather than horizontal. According to Rich Garrity, Stratasys president of the Americas, this system allows the building of “parts sized in feet or meters at a speed 10 times that of current systems.”

Powered materials (“micropellets” that measure approximately 0.5 mm long) are contained in canisters and fed out via a screw extruder. The arrangement allows the introduction of different materials into the part if required as well as long, unattended part production. The build process is such that the part being produced can be fed out of the machine (though it must be supported at the bottom) to a length as needed, something that heretofore hasn’t been possible. (One could imagine the creation of vehicle headliners with all manner of HVAC ducting and wiring channels being made with this process.)

The other is the Robotic Composite 3D Demonstrator. This unit is capable of printing parts from fiber-reinforced thermoplastic with an eight-axis motion system (Stratasys worked with Siemens (siemens.com) on both the design-to-manufacture and the motion control for the system). Parts can be built up without the need for support materials, which is ordinarily the case in printing operations.

What this means is that whereas composite parts are ordinarily produced in molding operations with pressure and heat (and in many cases with labor-intensive layup tasks), this permits the printing of composite parts of complex geometries (not only does the robot arm that wields the print head have its axes of motion, but the part is produced on a worktable that has axes, as well) out in the air.

Both of these demonstration systems allow the production of strong, lightweight parts in ways that provide much more throughput than has been the case up until now. And while they are just demonstration systems at this point, odds are better than good that they’ll be production ready in the not-too-distant future.